Aqueous coating material, especially aqueous filler or protective base against stones

ABSTRACT

Aqueous coating material comprising (A) water-dispersible hydroxy-functional binder component containing urethane groups, (B) water-dispersible binder component containing urethane groups and blocked isocyanate groups, (C) water-dispersible amino resin, and optionally (D) water-dispersible hydroxy-functional polyester, the binder component (B) being preparable by (B1) preparing a polyurethane prepolymer containing isocyanate groups from at least one polyol and at least one polyisocyanate, (B2) reacting the polyurethane prepolymer (B1) containing isocyanate groups with a chain extender to give a hydroxyl-containing chain-extended polyurethane prepolymer, (B3) reacting the hydroxyl-containing chain-extended polyurethane prepolymer (B2) with at least one polyisocyanate to give a further polyurethane prepolymer containing isocyanate groups, and (B4) blocking some or all of the isocyanate groups of the chain-extended polyurethane prepolymer (B3) containing isocyanate groups with a blocking agent to give a polyurethane containing blocked isocyanate groups, and then, where appropriate, (B5) reacting remaining free isocyanate groups in the polyurethane (B4) with a chain extender.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Ser. No. 10/018,155, now U.S.Pat. No. 6,620,511 filed on Dec. 14, 2001, which is a 371 National StageApplication of PCT/EP00/06106, filed 30 Jun. 2000, which claims priorityto DE 199 30 555.2, filed 2 Jul. 1999. U.S. Ser. No. 10/018,155, nowU.S. Pat. No. 6,620,511 is incorporated herein by reference.

The invention relates to an aqueous coating material, especially anaqueous surfacer or antistonechip primer, comprising (A) awater-dispersible hydroxy-functional binder component containingurethane groups, (B) a water-dispersible binder component containingurethane groups and blocked isocyanate groups, (C) a water-dispersibleamino resin, (D) optionally, a water-dispersible hydroxy-functionalpolyester, and (E) optionally, customary coatings additives. Theinvention further relates to a process for preparing such a coatingmaterial and to the uses thereof.

The provision of stonechip-resistant coatings on metallic substrates isof particular importance in the field of motor vehicle production.Stonechip-resistant coatings are applied in particular in the front areaand in the underbody area of a motor vehicle body. For reasons botheconomic and environmental, a coating material suitable for this purposeought to contain little or no organic solvents. Only (apart from powdercoating materials) aqueous coating materials are suitable for thispurpose.

A surfacer or antistonechip primer is subject to a number ofrequirements. It must be bakeable at a temperature of 120-160° C. andafter baking at such temperatures must exhibit outstanding propertiessuch as high stonechip resistance (particularly the combination ofmultiple and single chipping), effective adhesion to the primer coat, acathodic electrode coat, for example, and to the base coat, good fillingproperties (masking of the structure of the substrate) at a coatthickness of 20-35 μm, and an excellent appearance in the finalclearcoat. The combination of these properties is difficult to realizeon account of the fact that they are in part divergent properties, whereimproving one property automatically results in a deterioration inanother property. Such divergent or contradictory properties are, forexample, very good resistance to multiple chipping and to singlechipping, low coat thickness and very good filling power/topcoatappearance, low baking temperature and very good topcoat appearance, andlow baking temperature and high adhesion.

A coating material of the composition specified at the outset is knownfrom the reference EP 0 427 028 B1. In this material, component (B) isthe reaction product of a diisocyanate and a low molecular mass polyol.With the known coating material, not all of the abovementioned divergentproperties are obtained to a satisfactory extent. For a solventborneantistonechip primer, refer, for example, to the reference DE 31 08 861C2. Solventborne coating materials are unsatisfactory on environmentalgrounds alone. The reference DE 41 42 816 C1 discloses a surfacer forwhich the abovementioned components (A) and (B) are first of all reactedwith one another and then the reaction product is mixed with apolyisocyanate and a melamine resin to give the application-readycoating material. Technically speaking, this is a comparativelylaborious preparation. Moreover, even with the known coating material,not all of the abovementioned divergent properties are realized to asufficient extent. Further stonechip protection compositions are known,for example, from the references DE 38 05 629 C1 and DE 195 04 947 A1.

In opposition to the prior art specified at the outset, the technicalproblem on which the invention is based is to specify a coating materialwith which the desired divergent properties mentioned are obtained in away which, overall, meets all of the requirements.

To solve this technical problem, the invention teaches that the bindercomponent (B) specified at the outset is preparable by

(B1) preparing a polyurethane prepolymer containing isocyanate groupsfrom a polyol or mixture of polyols and from a polyisocyanate or mixtureof polyisocyanates,

(B2) reacting the polyurethane prepolymer (B1) containing isocyanategroups by means of a chain extender to give a hydroxyl-containingchain-extended polyurethane prepolymer,

(B3) reacting the hydroxyl-containing chain-extended polyurethaneprepolymer (B2) with a polyisocyanate or mixture of polyisocyanates togive a further polyurethane prepolymer containing isocyanate groups, and

(B4) blocking some or all of the isocyanate groups of the chain-extendedpolyurethane prepolymer (B3) containing isocyanate groups with ablocking agent to give a polyurethane containing blocked isocyanategroups, and then, where appropriate,

(B5) reacting remaining free isocyanate groups in the polyurethane (B4)with a chain extender.

Surprisingly, using the above-defined component (B) for use inaccordance with the invention in the coating material specified at theoutset, comprising components (A) and (C) and also, where appropriate,(D) and (E), gives a coating material which satisfies all of therequirements.

The binder component (B) for use in accordance with the invention isobtainable by reacting, in a first process step, at least one polyolwith at least one polyisocyanate to give the polyurethane prepolymer(B1) containing isocyanate groups.

Examples of suitable polyols are saturated or olefinically unsaturatedpolyesterpolyols having a number-average molecular weight of from 300 to5000, preferably from 1000 to 2000, and in particular from 1200 to 1600,which are prepared by reacting

sulfonated or unsulfonated saturated and/or unsaturated polycarboxylicacids or their esterifiable derivatives, together if desired withmonocarboxylic acids, and

saturated and/or unsaturated polyols, together if desired with monools.

Examples of suitable polycarboxylic acids are aromatic, aliphatic andcycloaliphatic polycarboxylic acids. Preference is given to usingaromatic and/or aliphatic polycarboxylic acids.

Examples of suitable aromatic polycarboxylic acids are phthalic acid,isophthalic acid, terephthalic acid, phthalic, isophthalic orterephthalic monosulfonate, or halophthalic acids, such as tetrachloro-and/or tetrabromophthalic acid, of which isophthalic acid isadvantageous and is therefore used with preference.

Examples of suitable acyclic aliphatic or unsaturated polycarboxylicacids are oxalic acid, malonic acid, succinic acid, glutaric acid,adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid,undecanedicarboxylic acid, dodecanedicarboxylic acid or dimer fattyacids or maleic acid, fumaric acid or itaconic acid, of which adipicacid, glutaric acid, azelaic acid, sebacic acid, dimer fatty acids andmaleic acid are advantageous and therefore used with preference.

Examples of suitable cycloaliphatic and cyclic unsaturatedpolycarboxylic acids are 1,2-cyclobutanedicarboxylic acid,1,3-cyclobutanedicarboxylic acid, 1,2-cyclopentanedicarboxylic acid,1,3-cyclopentanedicarboxylic acid, hexahydrophthalic acid,1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid,4-methylhexahydrophthalic acid, tricyclodecanedicarboxylic acid,tetrahydrophthalic acid or 4-methyltetrahydrophthalic acid. Thesedicarboxylic acids may be used both in their cis and in their trans formand also as a mixture of both forms.

Also suitable are the esterifiable derivatives of the abovementionedpolycarboxylic acids, such as, for example, their monoesters orpolyesters with aliphatic alcohols having from 1 to 4 carbon atoms orhydroxy alcohols having from 1 to 4 carbon atoms. Moreover, it is alsopossible to use the anhydrides of the abovementioned polycarboxylicacids, where they exist.

If desired it is possible, together with the polycarboxylic acids, touse monocarboxylic acids too, such as benzoic acid, tert-butylbenzoicacid, lauric acid, isononanoic acid, fatty acids of naturally occurringoils, acrylic acid, methacrylic acid, ethacrylic acid or crotonic acid,for example. As monocarboxylic acid it is preferred to use isononanoicacid.

Examples of suitable polyols are diols and triols, especially diols.Normally, triols are used in minor amounts alongside the diols in orderto introduce branches into the polyesterpolyols.

Suitable diols are ethylene glycol, 1,2- or 1,3-propanediol, 1,2-, 1,3-or 1,4-butanediol, 1,2-, 1,3-, 1,4- or 1,5-pentanediol, 1,2-, 1,3-,1,4-, 1,5- or 1,6-hexanediol, neopentyl hydroxypivalate, neopentylglycol, diethylene glycol, 1,2-, 1,3- or 1,4-cyclohexanediol, 1,2-, 1,3-or 1,4-cyclohexanedimethanol, trimethylpentanediol,ethylbutylpropanediol, or the positionally isomeric diethyloctanediols.These diols may also be used per se for the preparation of thepolyurethanes (A) for inventive use.

Further examples of suitable diols are diols of the formula I or II:

in which R¹ and R² each represent an identical or different radical andstand for an alkyl radical having from 1 to 18 carbon atoms, an arylradical or a cycloaliphatic radical, with the proviso that R¹ and/or R²may not be methyl;

in which R³, R⁴, R⁶ and R⁷ each represent identical or differentradicals and stand for an alkyl radical having from 1 to 6 carbon atoms,a cycloalkyl radical or an aryl radical and R⁵ represents an alkylradical having from 1 to 6 carbon atoms, an aryl radical or anunsaturated alkyl radical having from 1 to 6 carbon atoms, and n iseither 0 or 1.

Suitable diols I of the general formula I are all propanediols of theformula in which either R¹ or R² or R¹ and R² is not equal to methyl,such as 2-butyl-2-ethylpropane-1,3-diol,2-butyl-2-methylpropane-1,3-diol, 2-phenyl-2-methylpropane-1,3-diol,2-propyl-2-ethylpropane-1,3-diol, 2-di-tert-butylpropane-1,3-diol,2-butyl-2-propylpropane-1,3-diol,1-dihydroxymethylbicyclo[2.2.1]heptane, 2,2-diethylpropane-1,3-diol,2,2-dipropylpropane-1,3-diol or 2-cyclohexyl-2-methylpropane-1,3-dioland others, for example.

As diols II of the general formula II it is possible, for example, touse 2,5-dimethylhexane-2,5-diol, 2,5-diethylhexane-2,5-diol,2-ethyl-5-methylhexane-2,5-diol, 2,4-dimethylpentane-2,4-diol,2,3-dimethylbutane-2,3-diol, 1,4-(2′-hydroxypropyl)benzene and1,3-(2′-hydroxypropyl)benzene.

Of these diols, hexanediol and neopentyl glycol are particularlyadvantageous and are therefore used with particular preference.

The abovementioned diols may also be used per se for the preparation ofthe polyurethane prepolymers (B1) containing isocyanate groups.

Examples of suitable trials are trimethylolethane, trimethylolpropane orglycerol, especially trimethylolpropane.

The abovementioned triols may also be used per se for the preparation ofthe polyurethane prepolymers (B1) containing isocyanate groups (cf. thepatent EP-A-0 339 433).

If desired, minor amounts of monools may be used as well. Examples ofsuitable monools are alcohols or phenols such as ethanol, propanol,n-butanol, sec-butanol, tert-butanol, amyl alcohols, hexanols, fattyalcohols, allyl alcohol or phenol.

Especially advantageous polyesterpolyols result if the monomers areselected from the group consisting of isophthalic acid, dimer fattyacids, and hexanediol.

The polesterpolyols may be prepared in the presence of small amounts ofan appropriate solvent as entrainer. Entrainers used include, forexample, aromatic hydrocarbons, such as particularly xylene and(cyclo)aliphatic hydrocarbons, e.g., cyclohexane or methylcyclohexane.

Further examples of suitable polyols are polyesterdiols which areobtained by reacting a lactone with a diol. They are notable for thepresence of terminal hydroxyl groups and repeating polyester units ofthe formula —(—CO—(CHR⁸)_(m)—CH₂—O—)—. In this formula the index m ispreferably from 4 to 6 and the substituent R⁸=hydrogen, an alkyl,cycloalkyl or alkoxy radical. No one substituent contains more than 12carbon atoms. The total number of carbon atoms in the substituent doesnot exceed 12 per lactone ring. Examples thereof are hydroxycaproicacid, hydroxybutyric acid, hydroxydecanoic acid and/or hydroxystearicacid.

For the preparation of the polyesterdiols preference is given to theunsubstituted epsilon-caprolactone, in which m has the value 4 and allR⁸ substituents are hydrogen. The reaction with lactone is started bylow molecular mass polyols such as ethylene glycol, 1,3-propanediol,1,4-butanediol or dimethylolcyclohexane. It is, however, also possibleto react other reaction components, such as ethylenediamine,alkyldialkanolamine or else urea, with caprolactone. Further suitablehigh molecular mass diols include polylactamdiols, prepared by reacting,for example, epsilon-caprolactam with low molecular mass diols.

Further examples of suitable polyols are polyetherpolyols, especiallythose having a number-average molecular weight of from 400 to 5000, inparticular from 400 to 3000. Highly suitable polyetherdiols are, forexample, polyetherdiols of the general formula H—(O—(CHR⁹)_(o)—)_(p)OH,in which the substituent R⁹=hydrogen or is a lower, unsubstituted orsubstituted alkyl radical, the index o=2 to 6, preferably 3 to 4, andthe index p=2 to 100, preferably 5 to 50. Cited as particularly highlysuitable examples are linear or branched polyetherdiols such aspoly(oxyethylene) glycols, poly(oxypropylene) glycols andpoly(oxybutylene) glycols.

The polyetherdiols should on the one hand not introduce excessiveamounts of ether groups, since otherwise the polyurethanes (B) forinventive use that are formed undergo incipient swelling in water. Onthe other hand, they may be used in amounts which ensures the nonionicstabilization of the polyurethanes (B). In that case they serve as thefunctional nonionic groups (b3) described below.

In order to ensure dispersibility of the binder component (B) for use inaccordance with the invention in an aqueous medium, not only are thepolyols incorporated but also compounds by means of which stabilizing(potentially) ionic and/or nonionic functional groups are introduced.Suitable groups of this kind are

(b1) functional groups which can be converted into cations byneutralizing agents and/or quaternizing agents, and/or cationic groups,or

(b2) functional groups which can be converted into anions byneutralizing agents, and/or anionic groups, and/or

(b3) nonionic hydrophilic groups.

Examples of suitable functional groups (b1) for inventive use which maybe converted into cations by neutralizing agents and/or quaternizingagents are primary, secondary or tertiary amino groups, secondarysulfide groups or tertiary phosphine groups, especially tertiary aminogroups or secondary sulfide groups.

Examples of suitable cationic groups (b1) for inventive use are primary,secondary, tertiary or tertiary sulfonium groups or quaternaryphosphonium groups, preferably quaternary ammonium groups or quaternaryammonium groups, tertiary sulfonium groups, but especially tertiarysulfonium groups.

Examples of suitable functional groups (b2) for inventive use which maybe converted into anions by neutralizing agents are carboxylic acid,sulfonic acid or phosphonic acid groups, especially carboxylic acidgroups.

Examples of suitable anionic groups (b2) for inventive use arecarboxylate, sulfonate or phosphonate groups, especially carboxylategroups.

Examples of suitable neutralizing agents for functional groups (b1)convertible into cations are organic and inorganic acids such as formicacid, acetic acid, lactic acid, dimethylolpropionic acid, citric acid,sulfuric acid, hydrochloric acid or phosphoric acid.

Examples of suitable neutralizing agents for functional groups (b2)convertible into anions are ammonia, ammonium salts, such as ammoniumcarbonate or ammonium hydrogen carbonate, for example, and also amines,such as trimethylamine, triethylamine, tributylamine, dimethylaniline,diethylaniline, triphenylamine, dimethylethanolamine,diethylethanolamine, methyldiethanolamine, triethanolamine and the like,for example. The neutralization may take place in organic phase or inaqueous phase. A preferred neutralizing agent used isdimethylethanolamine.

The overall amount of neutralizing agent used in the coating compositionof the invention is chosen so that from 1 to 100 equivalents, preferablyfrom 50 to 90 equivalents, of the functional groups (b1) or (b2) of thepolyurethane (A) for inventive use are neutralized.

Of these functional (potentially) ionic groups (b1) and (b2) andfunctional nonionic groups (b3), the (potentially) anionic groups (b2)are advantageous and are therefore used with particular preference.

The introduction of (potentially) anionic groups (b2) into thepolyurethane molecules takes place by way of the incorporation ofcompounds which contain in the molecule at least one isocyanate-reactivegroup and at least one group capable of forming anions; the amount to beused may be calculated from the target acid number.

Examples of suitable compounds of this kind are those which contain twoisocyanate-reactive groups in the molecule. Suitable isocyanate-reactivegroups are, in particular, hydroxyl groups, and also primary and/orsecondary amino groups. Accordingly, it is possible, for example, to usealkanoic acids having two substituents on the alpha carbon atom. Thesubstituent may be a hydroxyl group, an alkyl group or, preferably, analkylol group. These alkanoic acids have at least one, in general from 1to 3, carboxyl groups in the molecule. They have from 2 to about 25,preferably from 3 to 10, carbon atoms. Examples of suitable alkanoicacids are dihydroxypropionic acid, dihydroxysuccinic acid anddihydroxybenzoic acid. One particularly preferred group of alkanoicacids are the alpha,alpha-dimethylolalkanoic acids of the generalformula R¹⁰—C(CH₂OH)₂COOH, in which R¹⁰ stands for a hydrogen atom or analkyl group having up to about 20 carbon atoms. Examples of especiallysuitable alkanoic acids are 2,2-dimethylolacetic acid,2,2-dimethylolpropionic acid, 2,2-dimethylolbutyric acid and2,2-dimenthylolpentanoic acid. The preferred dihydroxyalkanoic acid is2,2-dimethylolpropionic acid. Examples of compounds containing aminogroups are alpha,alpha-diaminovaleric acid, 3,4-diaminobenzoic acid,2,4-diaminotoluenesulfonic acid and 2,4-diaminodiphenyl ether sulfonicacid.

Nonionic stabilizing poly(oxyalkylene) groups (b3) may be introduced aslateral or terminal groups into the polyurethane molecules. For thispurpose it is possible, for example, to use alkoxypoly(oxyalkylene)alcohols having the general formula R¹¹O—(—CH₂—CH¹²—O—)_(r) H in whichR¹¹ stands for an alkyl radical having from 1 to 6 carbon atoms, R¹²stands for a hydrogen atom or an alkyl radical having from 1 to 6 carbonatoms and the index r stands for a number between 20 and 75. (cf. thepatents EP-A-0 354 261 or EP-A-0 424 705).

Suitable polyisocyanates include in principle all customary and knownaliphatic, cycloaliphatic, aliphatic-cycloaliphatic, aromatic,aliphatic-aromatic and/or cycloaliphatic-aromatic polyisocyanates andpolyisocyanate adducts that are used in the paints sector, and are alsoreferred to as paint polyisocyanates.

Examples of suitable polyisocyanates are isophorone diisocyanate(=5-isocyanato-1-isocyanatomethyl-1,3,3-trimethylcyclohexane),5-isocyanato-1-(2-isocyanatoeth-1-yl)-1,3,3-trimethylcyclohexane,5-isocyanato-1-(3-isocyanatoprop-1-yl)-1,3,3-trimethylcyclohexane,5-isocyanato-(4-isocyanatobut-1-yl)-1,3,3-trimethylcyclohexane,1-isocyanato-2-(3-isocyanatoprop-1-yl)-cyclohexane,1-isocyanato-2-(3-isocyanatoeth-1-yl)cyclohexane,1-isocyanato-2-(4-isocyanatobut-1-yl)cyclohexane,1,2-diisocyanatocyclobutane, 1,3-diisocyanatocyclobutane,1,2-diisocyanatocyclopentane, 1,3-diisocyanatocyclopentane,1,2-diisocyanatocyclohexane, 1,3-diisocyanatocyclohexane,1,4-diisocyanatocyclohexane, dicyclohexylmethane 2,4′-diisocyanate,dicyclohexylmethane 4,4′-diisocyanate, liquid dicyclohexylmethanae4,4′-diisocyanate with a trans/trans content of up to 30% by weight,preferably 25% by weight, and in particular 20% by weight, obtainable byphosgenation of isomer mixtures of bis(4-aminocyclohexyl)methane or byfractional crystallization of commercialbis(4-isocyanatocyclohexyl)methane in accordance with the patentsDE-A-44 14 032, GB-A-1220717, DE-A-16 18 795 or DE-A-17 93 785;trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylenediisocyanate, hexamethylene diisocyanate, ethylethylene diisocyanate,trimethylhexane diisocyanate, heptamethylene diisocyanate ordiisocyanates derived from dimer fatty acids, such as are sold under thecommercial designation DDI 1410 by Henkel and described in the patentsWO 97/49745 and WO 97/49747, especially2-heptyl-3,4-bis(9-isocyanatononyl)-1-pentylcyclohexane, 1,2-, 1,4- or1,3-bis(isocyanatomethyl)cyclohexane, 1,2-, 1,4- or1,3-bis(2-isocyanatoeth-1-yl)cyclohexane,1,3-bis(3-isocyanatoprop-1-yl)cyclohexane, 1,2-, 1,4- or1,3-bis(4-isocyanatobut-1-yl)cyclohexane, m-tetramethylxylylenediisocyanate (=1,3-bis(2-isocyanatoprop-2-yl)benzene or tolylenediisocyanate.

Examples of suitable polyisocyanate adducts are polyurethane prepolymerscontaining isocyanate groups, which may be prepared by reacting polyolswith an excess of polyisocyanates and are preferably of low viscosity.It is also possible to use polyisocyanates containing isocyanurate,biuret, allophanate, iminooxadiazinedione, urethane, urea carbodiimideand/or uretdione groups. Polyisocyanates containing urethane groups, forexample, are obtained by reacting some of the isocyanate groups withpolyols, such as trimethylolpropane and glycerol, for example. In thiscase it is preferred to use the polyisocyanates described in detailabove.

Very particular preference is given to using mixtures of polyisocyanateadducts containing uretdione and/or isocyanurate groups and/orallophanate groups, especially isocyanurates, based in particular onhexamethylene diisocyanate, such as are formed by catalyticoligomerization of hexamethylene diisocyanate using appropriatecatalysts. The polyisocyanate constituent may otherwise also consist ofany desired mixtures of the free polyisocyanates exemplified.

In the preparation of the polyurethane prepolymer (B1) containingisocyanate groups, the isocyanate groups are preferably employed in amolar excess over the hydroxyl groups. It is of advantage in accordancewith the invention if the ratio of hydroxyl groups in the polyols toisocyanate groups in the polyisocyanates is from 1:6 to 1:1.1,preferably from 1:5 to 1:1.2, and in particular from 1:4 to 1:1.3. If itis ensured otherwise that the resulting polyurethane prepolymer (B1)contains isocyanate groups, it is also possible to employ the hydroxylgroups in excess.

In accordance with the invention, in a second process step, thepolyurethane prepolymer (B1) containing isocyanate groups is chainextended with a suitable chain extender, so that hydroxyl groups result.Suitable chain extenders include: at least one polyol having afunctionality of from 2 to 4, at least one polyamine and/or at least onealkanolamine. The use of polyols, polyamines and amino alcohols leads tothe molecular weight increase of the polyurethanes (B).

Suitable polyols for the chain extension are polyols having up to 36carbon atoms per molecule such as ethylene glycol, diethylene glycol,triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol,1,2-butylene glycol, 1,6-hexanediol, trimethylolpropane, castor oil orhydrogenated castor oil, ditrimethylolpropane ether, pentaerythritol,1,2-cyclohexanediol, 1,4-cyclohexanedimethanol, bisphenol A, bisphenolF, neopentyl glycol, neopentyl glycol hydroxypivalate, hydroxyethylatedor hydroxypropylated bisphenol A, hydrogenated bisphenol A or mixturesthereof (cf. also patents EP-A-0 339 433, EP-A-0 436 941, EP-A-0 517707).

Examples of suitable polyamines have at least two primary and/orsecondary amino groups. Polyamines are essentially alkylene polyamineshaving from 1 to 40 carbon atoms, preferably from about 2 to 15 carbonatoms. They may carry substituents which have no hydrogen atoms that arereactive with isocyanate groups. Examples are polyamines having a linearor branched aliphatic, cycloaliphatic or aromatic structure andcontaining at least two primary amino groups.

As diamines, mention may be made of hydrazine, ethylenediamine,propylenediamine, 1,4-butylenediamine, piperazine,1,4-cyclohexyldimethylamine, 1,6-hexamethylenediamine,trimethylhexamethylenediamine, menthanediamine, isophoronediamine(1-amino-3-amino-methyl-3,5,5-trimethylcyclohexane),4,4′-diaminodicyclohexylmethane, 4,4′-diaminodicyclohexane,m-xylylenediamine, p-xylylenediamine, or isomeric octanediamines.Preferred diamines are hydrazine, alkyl- or cycloalkyldiamines such aspropylenediamine and isophoronediamine.

It is also possible to use polyamines which contain more than two aminogroups in the molecule. In these cases, however, it must be ensured—forexample, by using monoamines as well—that crosslinked polyurethaneresins are not obtained. Polyamines of this kind which can be used arediethylenetriamine, triethylenetetramine, dipropylenediamine anddibutylenetriamine. An example to be mentioned of a monoamine isethylhexylamine (cf. also the patent EP-A-0 089 497).

Examples of suitable amino alcohols are ethanolamine,methylethanolamine, diisopropylamine, diethanolamine,N-methyldiethanolamine, hydroxyethoxyethylamine, polyetheraminols,aminomethylpropanol, trishydroxymethyl-aminomethane or triethanolamine.

Of these, the polyols having a functionality of 3 to 4 and/or the aminoalcohols which contain at least two hydroxyl groups, especiallydiethanolamine, are of particular advantage and are therefore used withparticular preference in accordance with the invention. The resultinghydroxyl-containing, chain-extended polyurethane prepolymer (B2) isreacted in a third process step with at least one polyisocyanate to givea further polyurethane prepolymer (B3) containing isocyanate groups.

Examples of suitable polyisocyanates are those described above.

In accordance with the invention, the polyurethane prepolymer (B3)containing isocyanate groups is reacted in a fourth process step with ablocking agent, so that some or all of its isocyanate groups becomemasked or blocked and the polyurethane (B4) containing blockedisocyanate groups, i.e., the binder component (B) for use in accordancewith the invention, is the result.

Examples of suitable blocking agents are the blocking agents known fromU.S. Pat. No. 4,444,954:

i) phenols such as phenol, cresol, xylenol, nitrophenol, chlorophenol,ethylphenol, t-butylphenol, hydroxybenzoic acid, esters of this acid, or2,5-di-tert-butyl-4-hydroxytoluene;

ii) lactams, such as ε-caprolactam, δ-valerolactam, γ-butyrolactam orβ-propiolactam;

iii) active methylenic compounds, such as diethyl malonate, dimethylmalonate, ethyl or methyl acetoacetate, or acetylacetone;

iv) alcohols such as methanol, ethanol, n-propanol, isopropanol,n-butanol, isobutanol, t-butanol, n-amyl alcohol, t-amyl alcohol, laurylalcohol, ethylene glycol monomethyl ether, ethylene glycol monoethylether, ethylene glycol monobutyl ether, diethylene glycol monomethylether, diethylene glycol monoethyl ether, propylene glycol monomethylether, methoxymethanol, glycolic acid, glycolic esters, lactic acid,lactic esters, methylolurea, methylolmelamine, diacetone alcohol,ethylenechlorohydrin, ethylenebromohydrin, 1,3-dichloro-2-propanol,1,4-cyclohexyldimethanol or acetocyanohydrin;

v) mercaptans such as butyl mercaptan, hexyl mercaptan, t-butylmercaptan, t-dodecyl mercaptan, 2-mercaptobenzothiazole, thiophenol,methylthiophenol or ethylthiophenol;

vi) acid amides such as acetoanilide, acetoanisidinamide, acrylamide,methacrylamide, acetamide, stearamide or benzamide;

vii) imides such as succinimide, phthalimide or maleimide;

viii) amines such as diphenylamine, phenylnaphthylamine, xylidine,N-phenylxylidine, carbazole, aniline, naphthylamine, butylamine,dibutylamine or butylphenylamine;

ix) imidazoles such as imidazole or 2-ethylimidazole;

x) ureas such as urea, thiourea, ethyleneurea, ethylenethiourea or1,3-diphenylurea;

xi) carbamates such as phenyl N-phenylcarbamate or 2-oxazolidone;

xii) imines such as ethyleneimine;

xiii) oximes such as acetone oxime, formaldoxime, acetaldoxime,acetoxime, methyl ethyl ketoxime, diisobutylketoxime, diacetylmonoxime,benzophenone oxime or chlorohexanone oximes;

xiv) salts of sulfurous acid such as sodium bisulfite or potassiumbisulfite;

xv) hydroxamic esters such as benzyl methacrylohydroxamate (BMH) orallyl methacrylohydroxamate; or

xvi) substituted pyrazoles, imidazoles or triazoles; and also

xvii) mixtures of these blocking agents, especially dimethylpyrazole andtriazoles, malonic esters and acetoacetic esters, or dimethylpyrazoleand succinimide.

The blocking agents are selected so that the blocked isocyanate groupsonly undergo deblocking, and enter into crosslinking reactions, inprecisely the temperature range within which the thermal crosslinking ofthe coating material of the invention is to take place, in particular inthe temperature range from 120 to 160° C.

Of the blocking agents described in detail above, the oximes xiii) inparticular meet the aforementioned condition, so that they are used withparticular preference in accordance with the invention. Of these, inturn, the ketoximes, especially methyl ethyl ketoxime, offer veryparticular advantages and are therefore used with very particularpreference.

The blocking agents are preferably employed in stoichiometric amounts.

Where free isocyanate groups are still present in the resulting blockedpolyurethane (B4), they are reacted in an optional fifth process stepwith at least one of the chain extenders described in detail above.

In terms of its method, the preparation of the binder component (B) foruse in accordance with the invention has no special features but insteadtakes place with the customary and known methods of preparingpolyurethanes preferably in an optionally water-miscible organic solventor solvent mixture which is not reactive toward isocyanates. Examples ofsuitable solvents are ketones such as methyl ethyl ketone or methylisobutyl ketone or cyclic amides such as N-methylpyrrolidone.

The binder component (B) for inventive use is present in the coatingmaterial of the invention advantageously in an amount of from 1 to 50%,preferably from 2 to 30%, with very particular preference from 2.5 to20%, and in particular from 3 to 10%, by weight based in each case onthe solids content of the coating material of the invention.

For its use as intended, the binder component (B) for inventive use isdispersed in an aqueous medium and, if desired, the organic solvents areremoved by distillation.

The aqueous medium comprises substantially water. In this context theaqueous medium may already contain the further components of the coatingmaterial of the invention that are described in detail below, (A), (C),(D) and/or (E) and/or, in minor amounts, other dissolved solid, liquidor gaseous, organic and/or inorganic substances of low and/or highmolecular mass. For the purposes of the present invention, the term“minor amount” refers to an amount which does not remove the aqueousnature of the aqueous medium.

The aqueous medium may also, however, comprise straight water.

It is of advantage in accordance with the invention to use straightwater. Further advantages result if the solids content of the resultingdispersion of the binder component (B) for inventive use is from 10 to60%, preferably from 20 to 55%, and in particular from 25 to 50%, byweight based in each case on the polyurethane dispersion (B).

As a further essential constituent the coating material of the inventioncomprises the water-dispersible, hydroxy-functional binder component (A)containing urethane groups.

A binder component (A) which can be used in the context of the inventionis preparable, for example, by reacting a polyol or mixture of polyolshaving a number-average molecular weight of from 100 to 5000, preferablyfrom 150 to 2000, with a polyisocyanate or mixture of polyisocyanates,the structure and proportions of the polyol and polyisocyanate beingselected subject to the proviso that the binder component (A) preferablyhas an OH number of from 30 to 160, more preferably from 60 to 110.

Examples of suitable polyols and polyisocyanates are those described indetail above.

It is preferred if the polyol used to prepare the binder component (A)is a polyesterpolyol which preferably has a number-average molecularweight of from 250 to 5000, most preferably from 350 to 2000.Advantageously, the monomers for preparing such a polyesterpolyol areflexibilizing. Flexibilizing monomers may be selected, for example, fromthe group consisting of “adipic acid, dimer fatty acids and hexanediol”.

Advantageous binder components (A) are obtained if use is also made ofthe compounds described in detail above by means of which stabilizing(potentially) ionic and/or nonionic functional groups are introduced,neutralizing agents and/or chain extenders.

In terms of its method, the preparation of the binder component (A) foruse in accordance with the invention has no special features but insteadtakes place with the customary and known methods of preparingpolyurethanes preferably in an optionally water-miscible organic solventor solvent mixture which is not reactive toward isocyanates. Examples ofsuitable solvents are ketones such as methyl ethyl ketone or methylisobutyl ketone or cyclic amides such as N-methylpyrrolidone.

The binder component (A) for inventive use is present in the coatingmaterial of the invention advantageously in an amount of from 1 to 70%,preferably from 2 to 50%, with very particular preference from 3 to 40%,and in particular from 5 to 30%, by weight based in each case on thesolids content of the coating material of the invention.

For its use as intended, the binder component (A) for inventive use isdispersed in an aqueous medium and, if desired, the organic solvents areremoved by distillation.

The aqueous medium comprises substantially water. In this context theaqueous medium may already contain the further components of the coatingmaterial of the invention that are described in detail below, (C), (D)and/or (E), the above-described binder component (B) for inventive useand/or, in minor amounts, other dissolved solid, liquid or gaseous,organic or inorganic substances of low and/or high molecular mass.

It is of advantage in accordance with the invention to use straightwater. Further advantages result if the solids content of the resultingdispersion of the binder component (A) for inventive use is from 10 to60%, preferably from 20 to 55%, and in particular from 25 to 50%, byweight based in each case on the polyurethane dispersion (A).

As component (C) it is possible to use any water-dilutable amino resin.Suitable in this context is any amino resin suitable for surfacers,topcoat materials or transparent clearcoat materials, or a mixture ofsuch amino resins, especially melamine-formaldehyde resins which arereactive toward OH groups at temperatures from 100° C. to 180° C.,preferably from 120 to 160° C. For further details, refer to RömppLexikon Lacke und Druckfarben, Georg Thieme Verlag, 1998, page 29,“Amino resins”, and the textbook “Lackadditive” [Additives for coatings]by Johan Bieleman, Wiley-VCH, Weinheim, N.Y., 1998, pages 242 ff., or tothe book “Paints, Coatings and Solvents”, second completely revisededition, edit. D. Stoye and W. Freitag, Wiley-VCH, Weinheim, N.Y., 1998,pages 80 ff. Also suitable are the customary and known water-dilutableamino resins some of whose methylol and/or alkoxymethyl groups have beendefunctionalized by means of carbamate or allophanate groups. Aminoresins of this kind are described, for example, in the patents U.S. Pat.No. 4,710,542 and EP-B-0 245 700 and also in the article by B. Singh andcoworkers, “Carbamylmethylated Melamines, Novel Crosslinkers for theCoatings Industry” in Advanced Organic Coatings Science and TechnologySeries, 1991, volume 13, pages 193 to 207.

The water-dilutable amino resin (C) for inventive use is present in thecoating material of the invention advantageously in an amount of from 1to 50%, more preferably from 2 to 40%, with particular preference from 3to 30%, and in particular from 4 to 20%, by weight based in each case onthe solids content of the coating material of the invention.

The binder component (B) which can be used optionally advantageously hasthe following properties: number-average molecular weight of up to 5000,preferably from 500 to 3000, and OH number of between 50 and 300,preferably between 100 and 250. It is advantageous to use a component(D) which is composed at least in part of an epoxy-resin-modified,water-dilutable polyester preparable by

(D1) using

(D1.1) at least one polycarboxylic acid containing at least threecarboxyl groups, or a reactive derivative of this acid, and/or

(D1.2) at least one polyol containing at least one carboxyl group and

(D1.3) at least one polycarboxylic acid containing two carboxyl groups,or a reactive derivative of this acid, and

(D1.4) at least one polyol

at least 10 mol %, preferably 30-70 mol %, of the components (D1.1),(D1.2), (D1.3) and (D1.4) used (based on (D1.1)+(D1.2)+(D1.3)+(D1.4)=100mol %) containing at least one (cyclo)aliphatic structural elementcontaining at least six carbon atoms

to synthesize a polyester which has a number-average molecular weight ofless than 2000, preferably from 500 to 1500, an acid number of from 35to 240, preferably from 50 to 120, an OH number of from 56 to 320,preferably from 80 to 200, and in which all (D1.1) and (D1.3) componentsare incorporated by condensation via at least two carboxyl groups, and

(D2) then reacting this polyester thus obtained with from 0.3 to 1.5,preferably from 0.5 to 1.0, equivalents per polyester molecule

(D2.1) of an epoxy resin which has an epoxide equivalent weight of from170 to 1000, preferably from 170 to 500, and is based on a bisphenol,preferably bisphenol A, and/or

(D2.2) a derivative of this epoxy resin that contains at least oneepoxide group per molecule

under reaction conditions in which substantially only carboxyl groupsreact with epoxide groups, to give an epoxy-resin-modified polyester,which following

(D3) neutralization of at least some of the free carboxyl groups ispresent in water-dilutable form.

A polyester of this kind is known from the reference EP 0 269 828 B1, towhich reference is made for further details.

The carboxyl groups of the polyester are supplied by components (D1.1)and/or (D1.2). The polyester may be synthesized using the carboxyl groupsuppliers (D1.1) or (D1.2) alone or using a mixture of components (D1.1)and (D1.2).

Taking into account the abovementioned requirements, it is possible inprinciple as component (D1.1) to use any polycarboxylic acid whichcontains at least three carboxyl groups and is suitable for preparingpolyesters, or a reactive derivative (e.g., anhydride, ester or halide)or a mixture of such acids and/or acid derivatives. Examples that may bementioned include trimellitic acid, trimesic acid(1,3,5,-benzenetricarboxylic acid), pyromellitic acid and trimeric fattyacids. Trimellitic acid is used with preference.

Taking into account the abovementioned requirements, it is possible inprinciple to use as component (D1.2) any carboxyl-containing polyolsuitable for preparing polyesters, or a mixture of such polyols, apolyol being understood to be an organic compound which carries at leasttwo hydroxyl groups. Advantageously, dimethylolpropionic acid is used as(D1.2) component.

Taking into account the abovementioned requirements, it is possible inprinciple as component (D1.3) to use any polycarboxylic acid containingtwo carboxyl groups which is suitable for preparing polyesters, and/or areactive derivative (e.g., anhydride, ester or halide) or a mixture ofsuch acids and/or acid derivatives. Examples of suitable acids that maybe mentioned are: phthalic acid, isophthalic acid, terephthalic acid,fumaric acid, maleic acid, endomethylenetetrahydrophthalic acid,succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid anddimeric fatty acids. Preference is given to using phthalic acid,isophthalic acid, adipic acid, and dimeric fatty acids.

Taking into account the abovementioned requirements, it is possible inprinciple as component (D1.4) to use any polyol suitable for preparingpolyesters, or a mixture of polyols, a polyol being understood to be anorganic compound which carries at least two hydroxyl groups. Examples ofsuitable polyols are ethylene glycol, propanediols, butanediols,pentanediols. Neopentyl glycol, hexanediols, diethylene glycol,glycerol, trimethylolethane, trimethylolpropane, pentaerythritol,dipentaerythritol, neopentyl glycol hydroxypivalate,2-methyl-2-propyl-1,3-propanediol, 2,2,4-trimethyl-1,3-pentanediol, and2,2,5-trimethyl-1,6-hexanediol. Preference is given to using neopentylglycol, 1,6-hexanediol, and neopentyl glycol hydroxypivalate.

The epoxy resins (D2.1) based on a bisphenol, preferably bisphenol A,generally comprise reaction products of bisphenols with epichlorohydrin.These epoxy resins are to have an epoxide equivalent weight of from 170to 1000, preferably from 170 to 500, and to contain preferably onaverage from one to two, with particular preference two, epoxide groupsper molecule.

It is also possible to use derivatives (D2.2) of these epoxy resins thatcontain at least one epoxide group per molecule. Suitable derivativeswhich may be used are reaction products, containing at least one epoxidegroup per molecule, of the abovementioned epoxy resins and a(cyclo)aliphatic monocarboxylic or polycarboxylic acid, preferably amonocarboxylic or polycarboxylic acid having a (cyclo)aliphaticstructural element containing at least six carbon atoms. The derivativesmay be prepared by reacting the epoxy resins in question with, forexample, polymeric—preferably dimeric—fatty acids, adipic acid, azelaicacid, dodecanedicarboxylic acid, long-chain monocarboxylic acids,tetrahydrophthalic acid or hexahydrophthalic acid, so as to givereaction products which still contain at least one epoxide group permolecule.

Very particularly preferred water-dilutable polyesters are obtained ifthe polyester synthesized in stage (D1) was reacted with from 0.3 to1.5, preferably from 0.5 to 1.0, equivalents per polyester molecule of areaction product (D2.2) containing at least one epoxide group permolecule, being the reaction product of an epoxy resin based on abisphenol, preferably bisphenol A, having an epoxide equivalent weightof from 170 to 1000, preferably from 170 to 500, and a (cyclo)aliphaticmonocarboxylic or polycarboxylic acid containing a (cyclo)aliphaticstructural element containing at least 18 carbon atoms, preferably apolymeric fatty acid, in particular a dimeric fatty acid.

Reaction between the polyester synthesized in stage (D1) with the epoxyresin or epoxy resin derivative (D2.1) and/or (D2.2) must be conductedsuch that essentially only the carboxyl groups of the polyester (D1) arereacted with the epoxide groups of the epoxy resin (D2) and such thatcompeting reactions, such as the reaction of hydroxyl groups withepoxide groups, for example, proceed only to a minor extent.

Examples of suitable reaction conditions are as follows: reactiontemperature 25-180° C., preferably 80-160° C. The reaction may beconducted in an inert solvent or in bulk and is advantageously catalyzedby basic catalysts, such as tertiary amines, for example.

Following neutralization (D3) of at least some of the carboxyl groupspresent in the epoxy-resin-modified polyester (D) using basic compounds,such as ammonia, aliphatic secondary and tertiary amines, such asdiisopropanolamine, dimethyl- and diethylaminoethanol and alsotrimethyl-, triethyl- and tripropylamine, preferably tertiary amines,the epoxy-resin-modified polyester (D) is present in water-dilutableform.

The dispersion of the polyester (D) in an aqueous medium takes place asdescribed above for the binder component (A) and (B). In this case,advantageously, the same or approximately the same solids contents areset.

In the coating material of the invention the polyester (D) may bepresent in an amount of from 1 to 50%, preferably from 2 to 40%, withparticular preference from 3 to 30%, and in particular from 5 to 20%, byweight based in each case on the solids content of the coating materialof the invention.

The coating material of the invention may further comprise customarycoatings additives (E) in effective amounts. The nature and amount ofthe additives (E) are guided primarily by the intended use of thecoating material of the invention. It is advantageous that theseadditives (E) are not volatile under the processing and applicationconditions of the coating material of the invention.

Where the coating material of the invention is used as topcoat materialor aqueous basecoat material, it comprises color and/or effect pigments(E) in customary and known amounts. The pigments (E) may consist oforganic or inorganic compounds and may impart effect and/or color. Thecoating material of the invention therefore ensures, owing to this largenumber of appropriate pigments (E), a universal breadth of use of thecoating materials and permits the realization of a large number of colorshades and optical effects.

As effect pigments (E) it is possible to use metal flake pigments suchas commercially customary aluminum bronzes, aluminum bronzes chromatedin accordance with DE-A-36 36 183, and commercially customary stainlesssteel bronzes, and also nonmetallic effect pigments, such as pearlescentpigments and interference pigments, for example. Examples of suitableinorganic color pigments (E) are titanium dioxide, iron oxides,Sicotrans yellow and carbon black. Examples of suitable organic colorpigments are Indanthrene blue, Cromophthal red, Irgazine orange, andHeliogen green.

Furthermore, the coating material of the invention may comprise organicand inorganic fillers (E) in customary and known, effective amounts.Examples of suitable fillers are titanium dioxide, carbon black,graphite, chalk, calcium sulfates, barium sulfate, silicates such astalc or kaolin, silicas such as Aerosil®, oxides such as aluminumhydroxide, iron oxides or magnesium hydroxide, or organic fillers suchas textile fibers, cellulose fibers, polyethylene fibers or wood flour.For further details, refer to Römpp Lexikon Lacke und Druckfarben, GeorgThieme Verlag, 1998, pages 250 ff., “Fillers”.

The coating materials of the invention that are used to producesurfacers or antistonechip primers contain these pigments and/or fillers(E) advantageously in an amount of from 10 to 80%, preferably from 15 to70%, with particular preference from 20 to 65%, and in particular from25 to 60%, by weight based in each case on the overall solids content ofthe inventive coating material.

The abovementioned additives (E) are omitted if the coating materials ofthe invention are used as clearcoat materials.

Examples of suitable additives (E) which may be present both in theinventive clearcoat materials and also in the topcoat, aqueous basecoatmaterials and surfacers and antistonechip primers are

UV absorbers;

free-radical scavengers;

crosslinking catalysts;

slip additives;

polymerization inhibitors;

defoamers;

emulsifiers, especially nonionic emulsifiers such as alkoxylatedalkanols and polyols, phenols and alkylphenols, or anionic emulsifierssuch as alkali metal salts or ammonium salts of alkanecarboxylic acids,alkanesulfonic acids, and sulfo acids of alkoxylated alkanols andpolyols, phenols and alkylphenols;

wetting agents such as siloxanes, fluorine compounds, carboxylicmonoesters, phosphoric esters, polyacrylic acids and their copolymers,or polyurethanes;

adhesion promoters;

leveling agents;

film formation auxiliaries such as cellulose derivatives;

flame retardants;

low molecular mass, oligomeric, and high molecular mass reactivediluents which are able to participate in the thermal crosslinking,especially polyols such as tricyclodecanedimethanol, dendrimericpolyols, hyperbranched polyesters, polyols based on metathesis oligomersor branched alkanes having more than eight carbon atoms in the molecule;

high-boiling organic solvents (“long solvents”);

rheology control additives, such as those known from the patents WO94/22968, EP-A-0 276 501, EP-A-0 249 201 or WO 97/12945; crosslinkedpolymeric microparticles, such as are disclosed, for example, in EP-A-0008 127; inorganic phyllosilicates such as aluminum magnesium silicates,sodium magnesium phyllosilicates and sodium magnesium fluorine lithiumphyllosilicates of the montmorillonite type; silicas such as Aerosils;or synthetic polymers containing ionic and/or associative groups such aspolyvinyl alcohol, poly (meth)acrylamide, poly(meth)acrylic acid,polyvinylpyrrolidone, styrene-maleic anhydride copolymers orethylene-maleic anhydride copolymers and their derivatives, orhydrophobically modified ethoxylated urethanes or polyacrylates; or

crosslinking agents such as compounds or resins containing anhydridegroups, compounds or resins containing epoxide groups,tris(alkoxycarbonyl-amino) triazines, compounds or resins containingcarbonate groups, blocked and/or nonblocked polyisocyanates,beta-hydroxyalkylamides, and also compounds containing on average atleast two groups capable of transesterification, examples being reactionproducts of malonic diesters and polyisocyanates or of esters andpartial esters of polyhydric alcohols of malonic acid withmonoiso-cyanates, such as are described in the European patent EP-A-0596 460.

Further examples of suitable coatings additives are described in thetextbook “Lackadditive” [Additives for coatings] by Johan Bieleman,Wiley-VCH, Weinheim, N.Y., 1998.

Where used, these additives (E), which may be present not only in theclearcoat materials of the invention but also in the topcoat materials,aqueous basecoat materials, and surfacers and antistonechip primers, arepresent in the coating material of the invention advantageously in anamount of up to 40%, preferably up to 30%, with particular preference upto 20%, and in particular up to 10%, by weight based in each case on thesolids content of the coating material of the invention.

The invention further teaches a process for preparing an above-describedcoating material of the invention, in which components (A), (B) and (C)and also, where used, (D) are prepared separately, and where components(A), (B) and (C) and also, where used, (D) are mixed and homogenized togive the ready-to-apply coating material. In detail, the component (A)may be prepared as a pigment paste prior to mixing with components (B)and (C) and also, where used, (D). Components (A) and (B) and also,where used, (C) are usually prepared in the form of aqueous dispersionsprior to mixing, the dispersion containing component (A) preferablybeing free from solvents.

Component (E) may either be admixed to one of components (A), (B) and(C) and also, where used, (D) before these components are mixed, to givea pigment paste, or may be admixed, preferably in the form of a pigmentpaste, to the coating material in the course of the mixing of components(A), (B) and (C) and also, where used, (D).

The coating material of the invention is suitable for producingsingle-coat or multicoat coating systems which absorb mechanical energyand/or provide color and/or effect on primed or unprimed substrates. Itis also suitable for producing single-coat or multicoat clearcoatsystems on primed or unprimed substrates or on the single-coat ormulticoat, coating systems which absorb mechanical energy and/or impartcolor and/or effect.

Suitable substrates include all article surfaces to be coated which areamenable to curing of the paint films present thereon using heat; thatis, for example, articles made of metals, plastics, wood, ceramic,stone, textile, fiber composites, leather, glass, glass fibers, glasswool and rock wool or mineral-bound and resin-bound building materials,such as plasterboard panels and cement slabs or roofing tiles.Accordingly, the coating material is highly suitable for applications inautomotive finishing the varnishing of furniture, and industrialcoating, including coil coating and container coating. In the context ofthe industrial coatings it is suitable for coating virtually all partsfor private or industrial use such as radiators, domestic appliances,small metal parts, hub caps or wheel rims.

The coating material of the invention is especially suitable forproducing paint systems which absorb mechanical energy without beingdestroyed in the process.

The invention accordingly teaches in particular the use of the coatingmaterial of the invention for producing a surfacer coat and/or anantistonechip primer on a primed or unprimed substrate and also forproducing a coated metallic substrate, preferably a coated motor vehiclebody or a coated motor vehicle body component. In one process forproducing a coated substrate it is preferred if first of all one primer,preferably an electrodeposition primer, is applied to the substrate andbaked and then the coating material of the invention is applied theretoand baked, after which a preferably aqueous basecoat material is appliedand, after flashing off if desired, is optionally overcoated with aclearcoat material, preferably a two-component clearcoat material, and,in the case of overcoating with a clearcoat material, said clearcoatmaterial is baked “wet on wet” together with the basecoat material.

In this context, the coating material of the invention is applied in awet film thickness such that after curing there results in the finishedsurfacer coat of the invention or the antistonechip primer of theinvention a dry film thickness of from 5 to 100, preferably from 10 to75, with particular preference from 15 to 55, and in particular from 15to 40, μm.

The coating material of the invention may be applied by any customaryapplication method, such as spraying, knife coating, brushing, flowcoating, dipping or rolling, for example. It is preferred to employspray application methods, such as compressed air spraying, airlessspraying, high-speed rotation, electrostatic spray application (ESTA),alone or in conjunction with hot spray application such as hot airspraying, for example. Applications may be conducted at temperatures ofmax. 70 to 80° Celsius, so that suitable application viscosities areachieved without any change in or damage to the coating material and itsoverspray (which may be intended for reprocessing) occurring during theshort period of thermal stress. For instance, hot spraying may beconfigured in such a way that the coating material is heated only verybriefly in the spray nozzle or shortly before the spray nozzle.

The spray booth which is used for application may be operated, forexample, with an optionally temperature-controllable circulation whichis operated with a suitable absorption medium for the overspray, anexample being the coating material itself.

The thermal curing also has no special features in terms of its methodbut instead takes place in accordance with the customary and knownmethods such as heating in a forced air oven or exposure to IR lamps.Advantageously, the thermal curing takes place at a temperature of from100 to 180° C. and with particular preference from 120 to 160° C. for atime of from 1 min up to 2 h, with particular preference from 2 min upto 1 h, and in particular from 3 min to 30 min. Where substrates areused which are able to withstand high thermal loads, thermalcrosslinking may also be conducted at temperatures above 180° C. Ingeneral, however, it is advisable not to exceed temperatures of 180° C.,and preferably not to exceed temperatures of 160° C.

The surfacer coats or antistonechip primers of the invention have anoutstanding, balanced profile of properties in which even divergentproperties such as, for example, very good multiple impact and singleimpact, low film thickness and very good filling power/topcoatappearance, low baking temperature and very good topcoat appearance, andlow baking temperature and high adhesion are realized simultaneously.

EXAMPLES AND COMPARATIVE EXPERIMENT Example 1

Preparation of a Component A

Example 1.1

Preparation of a Polyesterpolyol A1

492 g of adipic acid, 559 g of isophthalic acid and 1192 g of hexanediolwere weighed into a reactor equipped with stirrer, column and oilheating and were slowly heated to 220° C. The water of reactioneliminated was distilled off from the reaction mixture via a column. Thereaction was continued until an acid number of the solid resin of <5 isreached. The finished polyester has a viscosity of 1.9 dPas measured in70% dilution in butyl glycol.

Example 1.2

Preparation of a Polyurethane Dispersion A2

444 g of 4,4-dicyclohexylmethane diisocyanate (Desmodur W from Bayer),57 g of dimethylolpropionic acid, 44 g of neopentyl glycol and 185 g ofN-methylpyrrolidone were weighed into a reactor with stirrer, refluxcondenser and oil heating and were heated to 100° C. The NCO groupcontent was determined hourly. At an NCO content of 9.74% in thesolution, it was cooled to 85° C. and 1037 g of the polyester describedunder example 1.1 were added. The mixture was reheated to 100° C. andthe reaction was continued with measurement of the NCO content. When theNCO content of the solution was less than 0.2%, it was cooled to 85° C.and 37 g of dimethylethanolamine were added for neutralizing thecarboxyl groups. Then 1900 g of water were added. The resultingpolyurethane dispersion had a solids of 40% (measured in a forced airoven for 60 min at 130° C.), an acid number of 19.2 and a pH of 8.3(measured in 2:1 dilution in water).

Example 2

Preparation of a Component B

631.2 g of a polyesterdiol made from isophthalic acid, dimer fatty acidand hexanediol (number-average molecular weight Mn about 1400) and 60.4g of dimethylolpropionic acid were reacted with 354.4 g of4,4-dicyclohexylmethane diisocyanate (Desmodur W from Bayer) in 448.2 gof ethyl methyl ketone at 80° C. until the NCO content was constant.Then 33.1 g of diethanolamine were added and the reaction mixture washeld at 80° C. with stirring for 2 hours. After the temperature had beenlowered to 60° C., 108.9 g of trimerized hexamethylene diisocyanate(Basonat® HI 100 from BASF) and 54.4 g of methyl ethyl ketoxime wereadded and stirring was continued at 60° C. for 30 minutes. Then afurther 33.1 g of methyl ethyl ketoxime were added. The reaction mixtureis held at 60° C. for 1 hour more and then 20.0 g of diethanolamine and20 g of methyl ethyl ketone are added for chain extension. After theexothermic reaction had subsided, the temperature was held at 80° C.until an NCO content of <0.1% was reached. The product at this point hada cone-and-plate viscosity of 3.0-6.0 dpas, measured in 1:1 dilutionwith N-methylpyrrolidone at 23° C. and 1000 s⁻¹. Then 121 g of butylglycol were added. 70% of the carboxyl groups present were thenneutralized with diethanolamine at 80° C. and 1972 g of distilled waterwere added over the course of one hour, with vigorous stirring, andcomponent (B) was dispersed therein. Thereafter, the methyl ethyl ketonewas distilled off in vacuo and the dispersion was adjusted to a solidscontent of 37%.

Example 3

Preparation of a Component D

442.4 g of hexanediol and 166.6 g of a technical-grade dimeric fattyacid (dimer content at least 80%, trimer content not more than 20%) wereweighed into a reactor equipped with stirrer, column and oil heating andwere slowly heated to 130° C. Then a further 184.3 g of isophthalic acidwere added and heating was continued to 220° C. The water of reactioneliminated was distilled off from the reaction mixture via a column. Thereaction was continued until an acid number of 10.5 is reached.Following cooling to 140° C., 266.7 g of trimellitic anhydride wereadded in portions with stirring. The mixture was then heated to 150° C.and subjected to esterification until an acid number of 67.7 had beenreached. It was then cooled to 120° C. and diluted with butyl glycol soas to give a solution having a solids content of 85%. The 85% polyestersolution was heated to 140° C. and admixed in portions with 209.6 g ofan epoxy resin made from bisphenol A and epichlorohydrin, having anepoxy equivalent weight of 490. Reaction was then carried out at 140° C.until an acid number of 42.1 and an epoxy equivalent of more than 50 000had been reached. The product was then cooled to below 100° C. andneutralized with 64.6 g of NN-dimethylethanolamine. The reactionmaterial was then run off with vigorous stirring into 2000 g ofdeionized water which had been heated to 60° C. beforehand. Finally, thedispersion was adjusted to a solids content of 35% and a pH of 7.5.

Example 4

Preparation of the Pigment Dispersion of an Inventive Surfacer

400 g of the polyurethane dispersion described under example 1, 7.4 g ofAerosil® R972 (Degussa), 33 g of Bayferrox 3910® (Bayer), 100 g of talc10MO (TDL), 204 g of Ti-pure® R900 (Du Pont), 26.2 g of Sicomixschwarz®6190 (BASF), 60 g of Blancfix® N (Sachtleben) and 140 g of deionizedwater were treated in a dissolver for 30 minutes and then ground to afineness of 12-15 μm in a commercial bead mill operated in circulationmode. The temperature during grinding was at least 30° C., maximum 60°C. At least 7 theoretical circuits were run.

Example 5

Preparation of an Inventive Aqueous Surfacer

To 970.6 g of the pigment dispersion from example 4 there were added 7.6g of Additol® XW 395 (Vianova Resins), 408 g of the aqueous polyesterdescribed under example 3, 188 g of the aqueous polyurethane dispersiondescribed under example 2, 136 g of a water-dilutablemethanol-etherified melamine resin, 100 g of the aqueous polyurethanedispersion described under example 1, 0.6 g of dimethylethanolamine, 20g of butyl glycol, 20 g of butyl diglycol, 44 g of Byketol® WS (BykChemie) and 45.8 g of deionized water, with stirring. After the finalitem, homogenization was carried out for 1 hour. The composition wasadjusted with dimethylethanolamine to a pH of 7.5 and with deionizedwater to a viscosity of 60-100 s DIN 4 (Ford Cup). For application, aprocessing viscosity of 30 s DIN 4 was set using deionized water.

Example 6

Preparation of a Pigment Dispersion of an Aqueous Surfacer (ComparativeExample)

400 g of the aqueous polyester described under example 3., 7.4 g ofAerosil® R972 (Degussa), 33 g of Bayferrox® 3910 (Bayer), 100 g of talc10MO (TDL), 204 g of Ti-pure® R900 (Du Pont), 26.2 g of Sicomixschwarz®6190 (BASF), 60 g of Blancfix® N (Sachtleben) and 140 g of deionizedwater were treated in a dissolver for 30 minutes and then ground to afineness of 12-15 μm in a commercial bead mill operated in circulationmode. The temperature during grinding was at least 30° C., maximum 60°C. At least 7 theoretical circuits were run.

Example 7

Preparation of an Aqueous Surfacer (Comparative Experiment)

To 970.6 g of the pigment dispersion from example 6 there were added 7.6g of Additol® XW 395 (Vianova Resins), 508 g of the aqueous polyesterdescribed under example 3, 188 g of the aqueous polyurethane dispersiondescribed under example 2, 136 g of a water-dilutablemethanol-etherified melamine resin, 0.6 g of dimethylethanolamine, 20 gof butyl glycol, 20 g of butyl diglycol, 44 g of Byketol® WS (BykChemie) and 45.8 g of deionized water, with stirring. After the finalitem, homogenization was carried out for 1 hour. The composition wasadjusted with dimethylethanolamine to a pH of 7.5 and with deionizedwater to a viscosity of 60-100 s DIN 4 (Ford Cup). For application, aprocessing viscosity of 30 s DIN 4 was set using deionized water.

Example 9

Test Results

The coating materials prepared in this way were subjected to tests forthe properties of surfacer coats produced using them. The properties ofthe surfacer coats were tested in a multicoat system familiar to theskilled worker, which can be produced from a commercial electrocoat, theinventive aqueous surfacer from example 5 or the comparative surfacerfrom example 7, a commercial aqueous basecoat material and a commercial2K clearcoat material, the aqueous basecoat material and the 2Kclearcoat material being applied by the technique known as thewet-on-wet technique without baking in between.

The results of the tests can be found in the table.

TABLE Test results Properties Example 5 Example 7 Example 9.1:Application of the surfacer in a film thickness of 20 μm, bakingtemperature 155° C. Ball shot (material removed in mm)^(a)) 6 8 Multipleimpact VDA (rating)^(b)) 2 2 Topcoat appearance (rating)^(c)) 2 3Adhesion GT2 (rating)^(d)) 0 2 Example 9.2: Application of the surfacerin a film thickness of 35 μm, baking temperature 155° C. Ball shot(material removed in mm)^(a)) 8 13 Multiple impact VDA (rating)^(b)) 2 2Topcoat appearance (rating)^(c)) 2 3 Adhesion GT2 (rating)^(d)) 0 2Rating: 0 = good, 5 = poor ^(a))Paint test procedure LPV 2007.40.70.01from Daimler Chrysler ^(b))Paint test procedure LPV 2007.40.70.05 fromDaimler Chrysler ^(c))Visual assessment ^(d))Cross-cut test inaccordance with ISO 2409: 1994-10

Comparison of the respective test results shows that only the inventivecoating material of example 5 at baking temperatures below 160° C. givesa surfacer which passes both the multiple impact and the single impacttests with distinction and which even at comparatively low filmthickness exhibits very good topcoat appearance and very good adhesion.

What is claimed is:
 1. A method for making an aqueous coating materialcomprising: I. forming a water-dispersible binder component thatcontains groups comprising urethane groups and blocked isocyanate groupsby a method comprising: (1) reacting at least one polyol and at leastone first polyisocyanate to form a polyurethane prepolymer that containsgroups comprising isocyanate groups, (2) reacting the polyurethaneprepolymer that contains groups comprising isocyanate groups with afirst chain extender to give a hydroxyl-containing, chain-extendedpolyurethane prepolymer, (3) reacting the hydroxyl-containing,chain-extended polyurethane prepolymer with at least one secondpolyisocyanate to give a further polyurethane prepolymer that containsgroups comprising isocyanate groups, and (4) blocking at least a portionof the isocyanate groups of the chain-extended polyurethane prepolymerthat contains groups comprising isocyanate groups with a blocking agentto give a polyurethane that contains groups comprising blockedisocyanate groups, and if there are free isocyanate groups remaining,(5) reacting remaining free isocyanate groups in the polyurethane with asecond chain extender, adding water to the polyurethane; and II. mixingthe water-dispersible binder component with (A) a water-dispersedhydroxy-functional binder component that contains groups comprisingurethane groups, (B) a water-dispersible amino resin, (C) optionally, acoatings additive, and (D) optionally, a water-dispersiblehydroxy-functional polyester.
 2. The method of claim 1, wherein thewater-dispersible hydroxy-functional binder component has an OH numberof from 30 to 160 mg KOH/g.
 3. The method of claim 1, wherein thewater-dispersible hydroxy-functional binder component has anumber-average molecular weight of from 500 to 20,000.
 4. The method ofclaim 1, wherein the water-dispersible hydroxy-functional bindercomponent comprises a reaction product of at least one polyol having anumber-average molecular weight of from 100 to 5,000 with at least onepolyisocyanate the structure and proportions of the polyol andpolyisocyanate being selected subject to the proviso that thewater-dispersible hydroxy-functional binder component has an OH numberof from 30 to 160 mg KOH/g.
 5. The method of claim 4, wherein the polyolis a polyesterpolyol.
 6. The method of claim 5, wherein thepolyesterpolyol comprises a reaction product of adipic acid, at leastone dimer fatty acid, and hexanediol.
 7. The method of claim 1, whereinthe polyol comprises a reaction product of isophthalic acid, at leastone dimer fatty acid, and hexanediol.
 8. The method of claim 1, whereinthe polyol has a number-average molecular weight of from 1,000 to 2,000.9. The method of claim 1, wherein the first polyisocyanate and thesecond polyisocyanate are each independently at least one of adiisocyanate adduct that contains at least one isocyanurate group and adiisocyanate.
 10. The method of claim 1, wherein the blocking agent isan oxime.
 11. The method of claim 1, wherein the amino resin is amelamine-formaldehyde resin that is reactive toward OH groups attemperatures of from 100° C. to 180° C.
 12. The method of claim 1,wherein the water-dispersible hydroxy-functional polyester comprises atleast in part an epoxy-resin-modified, water-dilutable polyestercomprising a reaction product of i) a polyester and ii) an epoxy resinin an amount from 0.3 to 1.5 equivalents per polyester molecule, (D1)wherein the polyester comprises a reaction product of (D1.1) one of atleast one polycarboxylic acid that contains groups comprising at leastthree carboxyl groups and at least one reactive derivative of thispolycarboxylic acid, and (D1.2) optionally, at least one polyol thatcontains groups comprising at least one carboxyl group and (D1.3) one ofat least one polycarboxylic acid that contains groups comprising twocarboxyl groups, and at least one reactive derivative of thispolycarboxylic acid, and (D1.4) at least one polyol, wherein instructural units of a combined amount of (D1.1), (D1.2), (D1.3) and(D1.4) comprises at least 10 mol % of at least one (cyclo)aliphaticstructural element comprising at least six carbon atoms, wherein thepolyester has a number-average molecular weight of less than 2,000, anacid number of from 35 to 240 mg KOH/g, an OH number of from 56 to 320mg KOH/g, and in which all (D1.1) and (D1.3) are incorporated bycondensation via at least two carboxyl groups; (D2) wherein the epoxyresin comprises at least one of (D2.1) an epoxy resin that has anepoxide equivalent weight of from 170 to 1,000 and is based on abisphenol and (D2.2) a derivative of this epoxy resin that contains atleast one epoxide group per molecule; wherein, in the reaction,substantially only carboxyl groups react with epoxide groups to give anepoxy-resin-modified polyester, and wherein at least a portion of freecarboxyl groups are neutralized such that the water-dispersiblehydroxy-functional polyester is water-dilutable.
 13. The method of claim1 further comprising applying one coat of the coating material to aprimed or unprimed substrate.
 14. The method of claim 13, wherein thecoat is at least one of a surfacer coat, an antistonechip coat, a colortopcoat, an effect topcoat, a color and effect topcoat, an aqueousbasecoat, and a clearcoat, and wherein the at least one coat is anenergy-absorbing paint system.
 15. The method of claim 1, wherein atleast two of: I. the water-dispersible hydroxy-functional bindercomponent has an OH number of from 30 to 160 mg KOH/g; II. thewater-dispersible hydroxy-functional binder component has anumber-average molecular weight of from 500 to 20,000; III. thewater-dispersible hydroxy-functional binder component comprises areaction product of at least one polyol having a number-averagemolecular weight of from 100 to 5,000 with at least one polyisocyanatethe structure and proportions of the polyol and polyisocyanate beingselected subject to the proviso that the water-dispersiblehydroxy-functional binder component has an OH number of from 30 to 160mg KOH/g; IV. the polyol comprises a reaction product of isophthalicacid, at least one dimer fatty acid, and hexanediol; V. the polyol has anumber-average molecular weight of from 1,000 to 2,000; VI. the firstpolyisocyanate and the second polyisocyanate are each independently atleast one of a diisocyanate adduct that contains at least oneisocyanurate group and a diisocyanate; VII. the blocking agent is anoxime; VIII. the amino resin is a melamine-formaldehyde resin that isreactive toward OH groups at temperatures of from 100° C. to 180° C.;and IX. the water-dispersible hydroxy-functional polyester comprises atleast in part an epoxy-resin-modified, water-dilutable polyestercomprising a reaction product of i) a polyester and ii) an epoxy resinin an amount from 0.3 to 1.5 equivalents per polyester molecule, (D1)wherein the polyester comprises a reaction product of (D1.1) one of atleast one polycarboxylic acid that contains groups comprising at leastthree carboxyl groups and at least one reactive derivative of thispolycarboxylic acid, and (D1.2) optionally, at least one polyol thatcontains groups comprising at least one carboxyl group and (D1.3) one ofat least one polycarboxylic acid that contains groups comprising twocarboxyl groups, and at least one reactive derivative of thispolycarboxylic acid, and (D1.4) at least one polyol, wherein instructural units of a combined amount of (D1.1), (D1.2), (D1.3) and(D1.4) comprises at least 10 mol % of at least one (cyclo)aliphaticstructural element comprising at least six carbon atoms, wherein thepolyester has a number-average molecular weight of less than 2,000, anacid number of from 35 to 240 mg KOH/g, an OH number of from 56 to 320mg KOH/g, and in which all (D1.1) and (D1.3) are incorporated bycondensation via at least two carboxyl groups; (D2) wherein the epoxyresin comprises at least one of (D2.1) an epoxy resin that has anepoxide equivalent weight of from 170 to 1,000 and is based on abisphenol and (D2.2) a derivative of this epoxy resin that contains atleast one epoxide group per molecule; wherein, in the reaction,substantially only carboxyl groups react with epoxide groups to give anepoxy-resin-modified polyester, and wherein at least a portion of freecarboxyl groups are neutralized such that the water-dispersiblehydroxy-functional polyester is water-dilutable.
 16. The method of claim15 further comprising applying one coat of the coating material to aprimed or unprimed substrate.
 17. The method of claim 16, wherein thecoat is at least one of a surfacer coat, an antistonechip coat, a colortopcoat, an effect topcoat, a color and effect topcoat, an aqueousbasecoat, and a clearcoat, and wherein the at least one coat is anenergy-absorbing paint system.